Solid stick corrosion inhibitors and a process for preventing corrosion of oil and gas well equipment



June 3, 1952 w, GRQSS HAL 2,599,384

SOLID STICK CORROSION INHIBITORS AND I A PROCESS FOR PREVENTING CORROSION OF OIL AND GAS WELL EQUIPMENT Filed April 8, 1950 2 SPEETS-SFEET l FIGI COMPOSITION OF VEHICLE moo/o M/W m 100% WAX GELLULOSE ETHER 0R ESTER AMORPHOUS HIGH-MELTING ORGANIC SOLVENT- SOLUBLE MINERAL WAX CELLULOSE DERIVATIVES PROPORTIONS ARE SELECTED FROM THE CLASS BY WEGHT OF ESTERS DERIVED FROM MONOCARBOXY ACIDS HAVING NOT MORE THAN 4 CARBON ATOMS' AND ETHERS DERIVED FROM ALCOHOLS NOT HAVING MORE THAN 4 CARBON ATOMS.

INVENTORS, WILLIAM F. GROSS,

CHARLES (3. ROGERS JR A TTORNEY.

June 3, 1952 w, GROSS ETAL 2,599,384

SOLID STICK CORROSION INHIBITORS AND A PROCESS FOR PREVENTING CORROSION OF OIL AND GAS WELL EQUIPMENT Filed April 8, 1950 27SHEETS-SHEET 2 FIGZ.

COMPOSITION OF HEAVY STICK CORROSION INHIBITOR WEIGHTWG 100% INVENTORS, WILLIAM F. GROSS, CHARLES C. ROGERSJR BY MW ATTORNEY- l atented June 3, 1 952 SOLID STICK CORROSION INHIBITORS AND A PROCESS FOR PREVENTING CORRO- SION OF OIL AND GAS WELL EQUIPMENT William F. Gross, Webster Groves, Mo., and

Charles 0. Rogers, Jr., San Antonio, Tex., assignors to Petrolite Corporation, Ltd., Wilmington, Del., a corporation of Delaware Application April 8, 1950, Serial No. 154,824

8 Claims.

One object of our invention is to provide a novel process for preventing corrosion of metal equipment of oil and gas wells.

Another object of our invention is to provide a novel corrosion inhibitor that can be used successiully to inhibit corrosion of gas and oil well equipment that is difiicult or impossible to protect with conventional corrosion inhibitors.

More specfically, our invention is concerned with the use of a composition in the form of a solid, under ordinary atmospheric conditions, which makes it particularly adaptable and effective under certain conditions hereinafter described. The solid form enjoys the unusual property of having a specific gravity in excess of 1.5, which opens up an entirely new field of application and use.

As will be pointed out subsequently, the dense or extra-heavy corrosion-preventing solid in stick form which has been developed and used industrially, usually consists of not less than five components:

(a) The corrosion-preventing inhibitor per se;

(b) The weighting material; and

(c), (d) and (e) Three nonrelated amorphous solids, which, in combination and within the specific limits hereinafter pointed out, give a. suitable unit structure both from a physical and chemical standpoint.

Numerous products have been found to be successful in the inhibition of corrosion of ferrous alloys. These products, together with certain solutions, blends, or mixtures of these products in other materials, such as oils, waxes and resins, have been described in U. S. Patents Nos. 2,466,- 530, 2,468,163 and 2,466,517.

For purposes of convenience, the subsequent text appears in four sections, which, although not divided, obviously deal with varying phases of the invention. In the text immediately following there is a consideration of the problem as it appears in the oil and gas industry and the ous problems which represent an inherent and integral problem as far as the manufacture of these corrosion-preventing solids are concerned, and also, as far as their use is concerned. It is this particular part of the text which points out that the solution of the problem was beyond the usual approach available in a. situation of this kind. The fourth part of the text is concerned with the preparation of suitable corrosion-inhibiting solids in stick form, which have been proven to be of outstanding value in actual industrial use.

Where an oil well, for example, is so completed that the annular space between tubing and inside casing is open at the well bottom, an inhibitor is usually employed in liquid form. The liquid is conventionally fed into the well annulus by means of a motor-driven chemical injection pump, or it may be dumped periodically (e. g., once every day or two) into the annulus by means of a lubricator or other metering device.

Occasionally oil and gas wells are completed in such a manner that there is no opening between the casing and the bottom of the tubing, i. e., the annulus is not open at the well bottom. This results, for example, when the tubing is surrounded at some point by a packing held by the casing or earth formation below the casing. Such wells are considered to be packed or plugged-off," and where the annulus is filled with mud, mudded-off."

For treating wells with packed-01f tubing, the use of solid plugs or "sticks of inhibitor is especially convenient, although the well may be treated by a liquid under certain special conditions, 1. e., where large volumes of liquid may be intrdouced at one time, where it is permissible to keep the well closed in for extended periods of time, and where the tubing is relatively free of liquid at the time of treatment. In general, treatment of packed-oil wells is by means of solid organic inhibitors, usually molded or formed into rods or sticks. These may be prepared by blending the inhibitor with a mineral wax, asphalt, or resin in a proportion sufiicient to give a moderately hard and relatively high-melting solid (1. e., softening point above F. ASTM ring and ball method), which can be handled and fed into the well tubing conveniently by means of a lubricator.

However, quite frequently the completion or operating characteristics of an oil or gas well are such as to preclude the treatment for corrosion by liquids and also by the solid form of inhibitor of common density, i. e., a density of 1.0 or less. which is obtained by the use of waxes, asphalts,

inches in diameter (a size common in oil and gas wells) filled with a fluid of density. 1.0 (the ap proximate average density of. anoilebrine emulsion), a stick of inhibitor 1 inchesin diameter.

would require the following timefto' fall-5,000 feet:

r Minutes] Density of Stick 5000 is not practical to shut ina well for, the. purposes of introducing a material for periods longer than SQ-minutes, and impossibleior periods long r, th an24 hours, solids of a density less-than 1,5;3'I1Q;Qf;1ifl71e value. The successfulv introduction-of, an inhibitor, consequently depends entirely upon itsv density being 1,5, or preferably,

E119 ter Reierence is made to the aforementioned patent s. No. 2,466,530 in which. certain examples teach the manufacture of suitable inhibitors per se -,7 and certain examplesteach the manufacture of conventional sticks fromsuch inhibitors. For purposes ofconvenience-and-ior otherobvious reasons, certain information of said patent is herein repeated in substantially ex a mi rm. e c pt that ec rosio 'pr y nv INHIBITOR A 20 .partspf maleic anhydride and. 54 partsof an.-.equal molal mixture of octadecenyI and:octadecylamine were placed in.a. reaction. vessel eq-uippedwithgasinlet tube, stirrer, heater and take-.011 tube." The mixture was. brought to a temperatureof 180 C. and held forsix hours. During. thelast hour, a slowustream of nitrogen was passed. through the reactionimixtureto completenremoval of. water of reaction. About.3.3 parts..of water were obtained. On cooling, the,

product. was janhard, resinous solid, readily solublein benzol and other hydrocarbon solvents.

INHIBITOR B I -54-.parts. of octadecyl amine were I substituted 4 Corrosion-preventive composition No. 2

Parts Product of Inhibitor A 50 Petroleum resin (Velsicol) 25 High-meltingparafiin wax V 25 The above were melted together and cast into sticks as in Corrosion-preventive composition No. 1.

A t-first examination, addition of the weighting material would seem to be merely a physical hicle, with the vehicle consisting of only one ing material, and,veh icle) 'butthe vehiclefinmodification. Inv actual practice, it was found that there were innumerable problems presented in manufacture, packaging, use, storage, trans portation, etc.,..w h. h were not susceptible to solution by any. predeterminable processes or knowledge.

'Withoutattempting to note all these difliculties, at this particular time, it will be sufiicient to simply say that hundreds upon hundreds of samples Wereprepared, examined, and discarded for a variety of reasons hereinafter-noted indetail. Such examination started. in a manner that I was purely logical, to wit,'a tertiary mixture consisting of inhibitor, weighting material, and -ve componentj Hundreds of-samples; were so pre pared, using hundreds of the amorphous-solidsranging from-materialsuch as synthetic-resins to waxes, polymers; and various other materials within this, enormously wide category. These;

tests were invariably failuresa The next examinationagain'involved a tertiary system,-i. e., those in which thesanie mate: rials'were used as previously (inhibitor, weight stead ofbeing composed of a single component,

was composed of two components.- The two component vehicle involved two I broad classes Y of materials:

(a) A mixture of the large variety of materials previouslyenumerated; and I (b) Afmixture, of a single one o f-such mate rials with other products which normally could; notqserve as a vehicle, due to co stor to" some particular physical or chemical-property-which would, it was hoped, modify the. primary vehicle component.

One example of such modifier was shellac. Obviously, shellac, beingbrittle, could not serve as'a vehicle per se but'it washoped that shellac or similar materialswould modify in a desirable; manner one or more of the hundreds of; amor-x phous resinousmaterials under examination,

The third examination wasalso concerned with a tertiary mixture, the vehicle of which fell into, 1

threeclasses;

forthezmixture of amines of Inhibitor A. Otherwise-;th'e procedure i identical-with that of In:-.

hibitor Aimmediatelypreceding.

canos wrw fi mmiii c va Parts Product of Inhibitor B 70 Ozokeritei'wax 30 habp ew re m t d t e t eransi castint nindsrsim i ehin d meter iii-inches long.

An adm ur of h imar veh cle w t two] difierent vehicle vadditives;

(b) An admixture of two primary vehiclemediawith one vehicle additive; and

(c) The mixture of threedifierent vehicleprin cipal media: without. any additive.

i e tin b l ni di e ir m hat has been... saidjirnmediatelypreceding that there was abs lutely n'obasis for the selection of an appro- Theseaiesuitable' for dropping down the tubingl ii -ti e.

te. eh l w nt-Pu e ance new lent.

' a at r r qt esb snsus e t e previous1y is an fever-simplification; of a rather involved procedure. In the preferred form the vehicle contains three components and the fi n ished sticlgcontains five components; i. e., the three-componentvehicle, plusthe inhibitor, y

the Wa st-therew- Having developed a vehicle, which, in absence of inhibitor and weighting agent, seemed to have approximately the correct physical and chemical properties, the next step was to modify the threecomponent vehicle (as far as the preferred form goes) so as to still exhibit the desired properties in presence of the weighting agent and inhibitor.

All of this is made plain by reference to the two hereto attached charts designated Figures 1 and 2..

Figure 1 is a conventional figure, which shows three constituents of the preferred vehicle on the basis of 100% by weight. One constituent is a thermoplastic, non-saponiflable hydrocarbon resin having a melting point in excess of approximately 225 F., described more fully elsewhere; the second apex indicates an amorphous wax, such as is described elsewhere, and the third component is a cellulose ether or ester of the kind described elsewhere. Note that the vehicle, based on these three components, is limited to the four-sided area defined approximately by points I, 2, 3 and 4.

Reference is now made to Figure 2 which is again a three component system, in which the vehicle, the inhibitor and the weighting agent comprise the system. Here again, notice that the final composition represents a comparatively small four-sided area in the triangular graph, and defined approximately by points I, 2, 3 and 4. This presentation involving the two triangular graphs, in efiect, presents in a shorthand fashion, the diificulties encountered as enumerated subsequently.

The successful weighted form of inhibitor has been developed after many hundreds of experimental molds were discarded. It is believed desirable that a weighted stick should have a uniform density of at least 1.5, and preferably, 2.0 or more. This is accomplished by incorporating a weighting material which should exhibit the following characteristics: The weighting material should be of high density, so that it occupies as small a volume of the stick as possible, and yet will increase the density of the total mixture to the desired value; the weighting material should be in such a form as to allow for an even distribution throughout the stick, resulting in a uniform density; the weighting material should not otherwise affect the desirable physical properties of the stick, such as increase in brittleness, stickiness, or tack, or appreciably alter the solvent characteristics of the stick or its melting point; the weighting material should be chemically inert towards the other ingredients and especially toward the inhibiting compound, and should be in itself non-corrosive; and the weighting material should not cause the stick to be poisonous or toxic, nor should it have any adverse effect on the operation of oil or gas wells, or their surface equipment, or upon their production.

Other obvious limitations are apparent, but are so numerous they need not be further specified, for example, the weighted stick form of inhibitor should be free from any deterioration or crystallization during aging; the surface of the stick should not be such as to cause firm adherence to the walls of the container, making dimcult the removal of the container before introduction of the stick into the well; the chenilcal properties of the weighted mixture should be such as to allow ready manufacture, i. e., no toxic fumes should be evolved; the material when molten should readily pour at not too elevated a temperature for easy casting, or the consistency should be right for molding or extruding at some convenient temperature; no foaming i should occur while molten, so that the stick, when cast, will be free of gas bubbles; after casting, the material should not shrink during cooling to the extent that a long neck is formed, extending inward from one end of the stick; the stick should be suiliciently tough to withstand normal handling and shipping without breaking; the melting point or softening point should be sufliciently high so that the stick remains hard and non-tacky to the touch after experiencing direct sun rays in summer; the solubility of the stick in hydrocarbons found in oil and gas wells, i. e., crude oil and kerosene, should be sufhciently low so that the stick would not be entirely dissolved during the first few hours after introduction down the well and the well returned to production.

As previously pointed out, the invention does not reside in the inhibitor per se, but in the particular form in which it is employed. Our preference is to use the inhibitors which have been described in Blair and Gross Patent No. 2,468,163, dated April 26, 1949. The particular inhibitors therein described represent substituted imidazolines selected from the class consisting of:

in which D represents a divalent, non-amino organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O, and N; D represents a divalent organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O, and 1:1, and containing at least one amino group; and R is a member of the class consisting of hydrogen and aliphatic and cycloaliphatic hydrocarbon radicals, with the proviso that at least one occurrence of R contains 8 to 32 carbon atoms.

More specifically, reference is made to the chemical formulae in said aforementioned Blair and Gross Patent No. 2,468,163, which depicts the actual composition and structure of a number of acceptable inhibitors. However, after considering the above formulae and what is said in the next paragraph immediately succeeding, it may be well to note that in the most generic description of the aforementioned Blair and Gross Patent No. 2,468,163 there are described compounds of the following composition:

occurrences of B be hydrogen. Such'derlvatives are obtained from polypropyleneamines, polybr tyJeneaminsmtm, inwhichythemtrogen atoms are; still: separated by; two carbon. atoms: Ourv preferenceiszto usertheimidazolines derived from thermostreadily availablepolyamines; to :wit, thepqlyethyleneamines; such as diethylenetriamine; triethylenetetramine, v tetraethylene pentamine and-pentaethylenehexamine;

Ashes, been.- pointed outzizrthez aforementioned: Blairsand: Gross. patents- -the imidazolines can; be used asr si ch; \orin theaformsofisalts; including; .for

example the salts; of monocai'boxy-..-' detergente== forming- .=-&oi1ds, suchi as.;the salts; ofhighenfatty acidsgabietic'w acid; rosin, naphthenic acid, etc. sinceithaimidazoiines.are basicincharacter; the: salts.-:ean;bea obtained; obviously by 'neutralization of the acid; on the saponification of:.the ester; or. byother well'knownzmeans;

byway; 01: illustration, we are:- includ ing the following examples of the inhibitor; as-

such-,7 and; subsequently; will include other: ex 1 v;

in which-R" is a hydrocarbon radieal'containing' 17 C atoms and 35 H atoms; and D'is-an'or ganieradical consisting ofthe elements, C, H, and N, and-consisting'of 2 ethylene r ups and 2 amine groups.-

A substituted imidazoline of the following-iormulaz /1STCH2 mac.

N-om

inwhich-Rf isahydrocarbon radical containing, a

19 atomsand -295H atoms; and *D is an organic radical consisting ofrtheelements QKH; and N; and consisting; of one ethylene-,groupand one; amine group.

A substituted imidazeline of the following formula:

rC 2 Ra-o Nrlac'nrv :FDII

m wnieninfiisga hydro arbo rad eali qntainineq 1 '4C.1a .om.s;m i3-; atoms; ar d-D" nan-or anic; radicalonsistingpmheeleme ta rlimdiliand:

aree re st r din: The m xture Example. abo e; to pr duce estmkawfih consisting: of 3 ethylene groups and; amine groups:

The inhibitors illustrated" above in: Exampleag- 1-4; partial salts of these'inhibitors with sel'ectbdfi acids; and others, are mixed and 'dissolved; im carefully. controlled amounts of organicand organic materials: in: order to=produce wproducti with the desired physical characteristics.

The: following examples -shows-typicallmethods; of manufacture of-rsucii productsrtheepamts usedi beingibit-Weigilt;-

Theifollowing ingredients:anesmelterttogetliem 59 par s: ofithe pe t rrosmete ontne mmbitnsi" tTE mnleB:

11; par s tr lit'e, Co p i n. Crown; O W 01 19 a gh ing icrocmste ine from domestic petroleum) 2""p ts Rg Dispers o s. na, Res n? (a high melting'thermoplastic resinobtaine lf y s ve t ex raction of U ahib e nc al;

When;- theabov mater als. a e: termed; 1:

ner. to: p oducer at; st ck :withi a; densityi'qi.

EXAMPLIEZa 59'-parts-of tliepartial' 'abietate'of th'e il-il imitbfidf Example 4- 10 parts Bareco' Gil Corp.- Be squarespee. we;

197195 (a: high 1 melting i microcrystalline ---rt'-ax' from domestic petroleum)" 20: parts: Vels'icol Corp: ABl I-S resin (a theremoplastic-hydroca-rbonresin obtained by polyw merization of unsaturated petroleum fractions) 19parts-ethyl cellulose;- 10-20 'centi'poises; stand ard' grade 7 The. materialstare meltedtogether, win-Example;

1a, above andL-then-BQL parts 1of. poslszderedharii'nrroxideware addedl atn150$? When. homogeneo s; the, mixtures is. casti,.as:in Example-1a, above, produmifiiv stickwitli a density of ;1 :6.

;par.ts. inhibitor otExample 2;

6 part oWarwick Wax-:Qo:.Mekon1195220o2'waxi- (aihishcmeltingzmicrocrystalline waxyfromrdoee m sticznetrolenmi Parts Ran @Americanz..Chemicals-5Resin; 3&210? (a{ thermoplastic: hydrocarboni resin oi; iodine numberi obtained :byrspolymerizationaofzi unsaturated hydrocarbons).

and grade Thematerials are meltediQ s th'erg ascin Ex im' plet1 a;above;and 'then l'2'9partscofffine f density of lfli EXAM LE-44 g} SO-partsof inhibitor of- Examplei' 10 parts of F; W." Steadman= Co. "DD /190 Wax (a high melting;microcrystalline' wax from domestic petroleum) 25-- parts Pan-American- Chemicals Pana-rez 652102 (a rthermoplastie. hydrocarboneresinofi 9 high iodine number obtained by polymerization of unsaturated hydrocarbons) 15 parts ethyl cellulose, 10-20 centipoises, standard grade The materials are melted together as in Example 1a, above, and then 129 parts of finely-divided litharge are stirred in. The mixture is cast as in Example 1a, above. to produce a stick with a density of 2.0.

EXANIPLE 5a 55 parts of the partial abietate of the inhibitor of Example 3 parts ozokerite wax parts Barrett Div., "Cumar Resin v2- coumarone indene resin) 15 parts ethyl cellulose, 10-20 centipoises, standard grade The materials are melted together as in Example 1a, above, and then 130 parts of finely-divided lead are stirred in. The mixture is cast as in Example 1a, above, to produce a stick with a density of 2.2.

EXAMI-"LE 6a The materials are melted together as in Example 1a, above, and then 129 parts of finely-divided litharge are stirred in. The mixture is cast as in Example la, above, to produce a stick with a a density of 2.0.

EXAWLE 7a parts of the partial rosinate of the inhibitor of Example2 10 parts F. W. Steadman Co. FWS 180/195 Wax (a high melting microcrystalline wax from domestic petroleum) 22 parts Neville Co. "Nevillac Hard resin (a phenol-coumarone-indene resin) 13 parts Tennessee Eastman Corp. cellulose acetate butyrate CAB 500-1 (the acetate-butyrate diester of cellulose) The materials are melted together as in Example 1a, above, and then 129 parts of finely-divided lltharge are stirred in. The mixture is cast as in Example 1a, above, to produce a stick with a density of 2.0.

EXAMPLE 8a parts 01 the partial rosinate of the inhibitor of Example 1 '7 parts Petrolite Corp. "Crown 500 Wax, 190/195 (a high melting microcrystalline wax from domestic petroleum) 20 parts Neville Co. "Nuba 2 resin (a phenolcoumarone -indene resin) 13 parts Tennessee Eastman Corp., cellulose acetate butyrate CAB 500-1 (the acetate-butyrate diester of cellulose) The materials are melted together as in Example In, above, and then 129 parts of finely-divided litharge are stirred in. The mixture is cast as in Example la, above, to produce a stick with a density of 2.0.

Paraez 10 EXAMPLE 9a 55 parts of inhibitor of Example 3 10 parts Petrolite Corp. Crown 1035 Wax (a high melting mlcrocrystalline wax from domestic petroleum) 20 parts Neville C0. Neville R-lO phenol-coumarone -indene resin) 15 parts ethyl cellulose, 10-20 centipoises, standard grade The materials are melted together as in Example resin (a -la, above, and then 129 parts of finely-divided litharge are stirred in. The mixture is cast as in Example la, above, to produce a stick with a density 01' 2.0.- 1

EXAMPLE 10a 55 parts of the partial abietate of the inhibitor of Example 4 10 parts 'ozokerite 20 parts Velsicol Corp. Velsicol AB-11-2 resin (a thermoplastic hydrocarbon resin obtained 'by polymerization of unsaturated hydrocarbons) 15 parts Tennessee Eastman Corp. cellulose acetate butyrate CAB 500-1 (the acetatebutyrate diester of cellulose) The materials are melted together as in Example 1a, above, and then parts of finely-divided lead is stirred in. The mixture is cast as in Example 1 1, above, to produce a-stick with a. density oi. 2.2.

Reference is made to the class specified as consisting of cellulose derivatives, such as the esters of low molal monocarboxy acids and ethers derived from alcohols having not more than 4 carbon atoms. This class specifically includes .the organic solvent-soluble ethyl ethers, organic ((1) Ethers soluble in organic solvents; (b) Ethers soluble in water; and (c) Ethers soluble in alkali.

We employ the cellulose ethers of the kind which are ordinarily soluble in organic solvents. They should dissolve readily in the remaining two components of the vehicle, i. e., into wax-resin mixtures.

In preparing the solid stick form inhibitor, all that need be done is as follows: Select a suitable resin of the kind specified, such as a petroleum resin of the kind sold to replace coumarone-indene resins, or a coumarone-in dene resin, or a resin derived from brown coal. These are furnished, among others, by the following companies: the Neville Company, Pittsburg 25, Pa.; Barrett Division, 40 Rector St.. New York city, N. Y.; the Velsicol Co., Chicago, Illinois; the Pan-American Refining Co., Texas City, Texas; or the BBB Dispersions Division, Bound Brook, New Jersey. Select a suitable amorphous highmelting wax, such as ozokerite or wax sold by the Wax Division, Petrolite Corporation, Ltd., under the name of Crown Wax 500, 700, or 1035. Add tothis mixture van or- 111 ganic solvent-soluble :cellulose ether or ester which is soluble with the othertwo ingredients. Eel-est thejsnroportion so thearatios, by weight, comewithin-therpercentaee weights or. :compositions of the parallelogram defined by points :1, 2, 3 and! of :Figure :1. :All that lsrequiredis to melt this wax rand :resin, :and the zcellulose ether or ester has inotznelted, thel2l500ntinl16il0 stir the mixture until it is dissolvedthrough the entire massand. a homogeneous vehicle is obtained. Thenextstep is to combine the 've- "hicle with. animidazoline or its suitablepartial i-sailt of the kind specified, and also with a weighting material so the "final composition ;is

indicated by the percentage weights or compositions of the parallelogramdndicated by the v poi-nts 1,2,3 and' L in Figure Such mixture is stirred until thoroughly homogeneous and then poured into suitable molds without aperanittingany separation in :any :manner.

"lRleterence ls made to the previous examples "which illustrate the-manufacture of the stick inhibitor in a single one-step process. However, as an illustration of a two-step process in which the "vehicle is first prepared and subsequently mixed with the inhibitor and weighting material, the

following examples will serve, in which percentagesare byweight:

EXAMPLE lb 25% Velsicol'Corp. ABM-8 resin '(a thermoplastic hydrocarbon resin obtained by polymerization of unsaturated hydrocarbons) Bareco Oil Co. Be Square Spec. Wax

7 31907195 (a high melting mierocrystallinewax from domestic petroleum) ethyl cellulose, 10920 centipoises, standard iiiheanaterials areimixed togetheratfloo" 'C., until molten andhomogeneous.

' V EXAMPLE-211' i 911125333118 :DivHCumar Resin 'vz-a i (a'couma- 'rone-indene resin) 10% Retrolite, Corp. Crown 700 wax (a high melting microcrystalline wax from *domestic petroleum) 50%,Bthyl cellulose, 10-=20' cps. Standard {Ilie-materialsare blended together as in Example 1b, preceding.

EXAMPLE 3b 65% Pan American ffPanarez #l32l0 resin (a thermoplastic hydrocarbon resin .of high iodine number obtained by polymerization of unsaturated hydrocarbons) 10% War-wickWax Co. Mekon'195/200" wax a. f-hig-h' melting 'microcrystalline wax from domestic petroleum) Tennessee Eastman Corp. cellulose acetate- V50% .RBH Dispersions "@510 Resin Ia high .melting thermoplastic resin obtained 'by solvent extraction of Utah brown coal) 20% Petroli-te Com). Crown 7110 was (a high melting microerystalli-ne wax from domestic petroleum) ethyl cellulose, IO-2O cps.,.-stan'dai d The materials are blended together as'idE-xample lb, preceding.

EXAlVIPIJEJEb 40% Pan American Panarez #6-21'0 Resin (a thermoplastic hydrocarbon resin Q fl'ligh iodine number obtained bypolymerization of unsaturated hydrocarbons') I 20% FfWISteadman Co.""DD 185/190 was a high melting microcrystalline wax'from dome'stic petroleum) 40% :ethyl cellulose, 10-20 cps-standard The materials are blended together. as "hrExample lb, preceding.

Having obtained the vehicle-as described above, it can be stored for use or immediately combined, as illustrated "by the "following examples, in which percentages are byweieht:

' MP' ZLE 11c 20% imidazoline' l nh'ibitor 118% vehicleerrsxampleeb 62 'finely-dividedi-lead The vehicle and inhibitorflare iblendedltoge'ther at C. and the powdered'lead stirredinijmtil homogeneous, at which point the material is 'eas'trinto rods or'stleks.

128% 'partialrosinate 11f imidazolinerinhibitor 18% vehicle of Example 2?) 54% finely-divided Hie materials are blended andsti'ck cast' as'in Example 10, preceding.

28% partial abietate niimidazoline inhibitor 40% vehicle of Example 4b 56% finely-divided "litharg e The materials are blended and stick "cast: as l in Example 10, preceding.

In addition to the weighting materials em 13 ployed by way of illustration in the preceding examples (barium oxide, barium sulfate, powdered lead, and litharge), other dense materials in powder form may be equally useful in the formation of solid inhibitors with an average density of 1.5 or greater.

From considerations of availability and cost, and because of considerations already discussed, certain dense materials are preferred above others. Powdered lead metal and lead oxides are especially useful. Iron oxides would be equally useful if it were not for the fact that their use invalidates the control of corrosion rate by the analysis of produced brines for iron content.

In the appended claims the melting point of the waxes employed refers to the ASTM method for determination of melting point of petrolatum, Specification Dl2'7-30, which method is commonly accepted by the trade for the specification of melting point of mineral waxes and parafiins. The melting point of resins refers to the ASTM ring and ball method for the determination of softening point of bituminous materials, D36-26, which method is commonly accepted by the trade for the specification of melting point of resins.

' Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A high-melting solid stick-form corrosion inhibitor for oil, and gas well equipment, having a specific gravity in excess of 1.5 and being of the following composition: a) Weighting material selected from a member of the class consisting of lead oxide, barium sulfate, and metallic lead; and

(b) a member selected from the group consisting of substituted imidazoline and its partial salt saw lected from the class consisting of in which B is a member selected from the class consisting of hydrogen atoms and an alkyl radical having not over 2 carbon atoms, with the proviso that at least three occurrences of (B) be hydrogen. and X is selected from the class of hydrogen atoms, R, DR, and DR, in which D represents a divalent, non-amino, organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O. and N; D represents a divalent organic radical containing less than 25 carbon atoms composed of elements from the group consisting of C, H, O, and N, and containing at least one amino group, and R is a member of the class consisting of hydrogen and aliphatic and cycloaliphatic hydrocarbon radicals, with the proviso that at least one occurrence of R contains 8 to 32 carbon atoms; and (c) a vehicle; said ratio of ingredients being approximately within the weight percentages specified by the parrallelogram defined by points I, 2, 3, and 4 in Figure 2; with the further proviso that the vehicle (0) specified immediately above shall be composed of (1) and amorphous high melting mineral wax; (2) an organic solventsoluble cellulose derivative selected from the class of esters derived from monocarboxy acids having not more than 4 carbon atoms and ethers derived from alcohols not having more than 4 carbon atoms, and (3) a thermoplastic non-saponifiable hydrocarbon resin having a melting point in excess of approximately 225 F., selected from the class of coumarone-indene resins, coumaroneindene type petroleum resins, and resins obtained by the extraction of brown coal; and with the final proviso that said ratio of ingredients (1); (2); and (3), be approximately within the weight percentages specified by the parallelogram defined by points I, 2, 3 and 4 in Figure 1.

2. An inhibitor of the kind described in claim 1, wherein the resin employed is a, petroleum resin of the coumarone-indene type having a melting point of approximately 225 F. by the ring and ball method, and the wax is a high melting mineral wax derived from domestic petroleum and having a melting point (by A. S. T. M. D12'7-30 method for melting point of petrolatum) of approximately 190 F.-200 F.

3. An inhibitor of the kind described in claim 1, wherein the vehicle is composed of (1) a petroleum resin of the coumarone-indene type having a melting point of approximately 225 F. by the ring and ball method, (2) a high-melting mineral wax derived from domestic petroleum and having a melting point (by A. S. T. M. D12'I-30 method for meltin point of petrolatum) of approximately 190 F.200 F., and (3) is ethyl cellulose.

4. An inhibitor of the kind described in claim 1 wherein the vehicle is composed of (1) a petroleum resin of the coumarone-indene type having a melting point of approximately 225 F. by the ring and ball method, (2) a, high melting mineral wax derived from domestic petroleum and having a melting point (by A. S. T. M. D12'7-30 method for melting point of petrolatum) of approximately 190 F.-200 F., and (3) ethyl cellulose, and. the weighting material is litharge.

5. An inhibitor of the kind described in claim 1, wherein the vehicle is composed of (1) a petroleum resin of the coumarone-indene type having a melting point of approximately 225 F. by the ring and ball method, (2) a high melting mineral wax derived from domestic petroleum and having a melting point (by A. S. T. M. D12'7-30 method for melting point of petrolatum) of approximately 190 F.-200 F., and (3) ethyl cellulose, the weighting material is litharge, and the imidazoline is of the formula wherein R is a member of the class consisting of aliphatic and cycloaliphatic hydrocarbon radicals containing 8 to 32 carbon atoms.

6. An inhibitor of the kind described in claim 1, wherein the vehicle is composed of (1) a petroleum resin of the coumarone-indene type having a, melting point of approximately 225 F. by the ring and ball method, (2) a high-melting mineral wax derived from domestic petroleum and having a melting point (by A. S. T. M. D127-30 method for melting point of petrolatum) of approximately 190 F.-200 F., and (3) ethyl cellulose, the weighting material is litharge, and the imidazoline is of the formula N-CH,

:H4NHCgH4NH:

wherein R, is a member of the class consisting of aliphatic and cycloaliphatic hydrocarbon radicals containing 8 to 32 carbon atoms.

7. An inhibitor of the kind described in claim T5 1,; :w remY-me vehicle is composed 1) a ipetroleuni resii'i of theooumai'one-indene type heving a melting .poinbof'appreximately 225 F. --'Hy the: rii1g and ballmethod; (2) -ahigh-melting mineral wax derived from domestic petroleum and having a. melting point (by A. S. T. M. 131 -27-30 methodfor-meltin'g point of petrolatum) of "approximately 190 Fr-ZBO" F; and (3) ethyl 'eelliilose, the weighting material is lithargeand the imidazoline is of the formula N o'm ii-d \NQPHB iiiiNiioafi-ififiozfig-Nm "Whefeih 'R i sl'afihfil fi if 6f 'th' ei'ass consisting of 'eiph'a l' afl d yloeliphatic"hi dfocai'boh radi- "ls 'eoiita n ng- 8 i932 cj' rboh atoms.

I 8. fAn inhibitor of the-kind'desoribed in claim '1, wherein the vehicle is composed of (1 a .p ti oleiiiniesin of izl'ifeboumarone' ir'ldene type fh'fivlng a melting po'int'of approximately 225 F. -by' th'efriiig 'a'nd bll'me'thod, ('2) a. high melting "'rhiiieial wax d'e'riv'd {rem domestie getioleum and having a melting point (by A. S. T. M.

ofappioximately 190 Fs-ZOO" F. and (31 ethyl cellulose, the weighting-material is litharge, and the imidazoline is of the formula ir -0H2 \JTIL H1 7 mmNHmmNHommHcmmH,

wherein R is a-memberef the elass eensi'stigl of-aliphatic and eycloaliphatic hydrocarbon radicals containing 8 to 32 carbon atoms.

3- QRQ LS-A CHARLES C. ROGERS, JR.

REFERENCES GIIED Thefollowing references are of 'reeereiin the file of this patent:

UNITED STATES FATENTS Number Name Date Re. 23,227 Blair et-al. May 9, 1950 

1. A HIGH-MELTING SOLID STICK-FORM CORROSION INHIBITOR FOR OIL, AND GAS WELL EQUIPMENT, HAVING A SPECIFIC GRAVITY IN EXCESS OF 1.5 AND BEING OF THE FOLLOWING COMPOSITION: (A) WEIGHTING MATERIAL SELECTED FROM A MEMBER OF THE CLASS CONSISTING OF LEAD OXIDE, BARIUM SULFATE, AND METALLIC LEAD; AND (B) A MEMBER SELECTED FROM THE GROUP CONSISTING OF SUBSTITUTED IMIDAZOLINE AND ITS PARTIAL SALT SELECTED FROM THE CLASS CONSISTING OF 